add support for resend an invite email

db: email comparison should be case insensitive

Fix cross compilation

When reading migrations from files, sql-migrate attempts to split
SQL statements. The parsing logic does not handle $BODY$ statements
and broke when the migration included one.

Replace go-bindata with a small migration generation script and use
in memory migrations instead.

Fixes #338

*: remove unused code

This change has no functional changes, it only removes dead code.

This change solves the User's API problem when you want to create an user that its email hasn't been verified yet but it exist.
At now, you can resend invitation email using endpoint /users/{id}/resend-invitation

Fixes #184

db: only allow one open connection for in memory databases

examples: set example app flag defaults to work with --no-db mode

functional: don't fail if postgres or ldap isn't available

user: fix password info JSON encoding to survive round trips

PasswordInfos are marshaled when storing them in the database as
part of the local connector. However, the custom unmarsheler
defined could not unmarshal the standard marshling of this struct.

Add a struct tag to the Password field to correct this.

Closes #332

sqlite3 in memory databases do not support concurrent writes. Limit
number of open connections to prevent race conditions.

move to sqlite3 for --no-db mode and tests

Documentation: update roadmap with issue and PR numbers

Closes #299

*: add go 1.6 to CI

connector_ldap: Make constants for default values, simplify logic

Get DN from entry, not entryDN attribute

Not all LDAP servers have entryDN available as an attribute. Reading up on
https://tools.ietf.org/html/rfc5020 tells me that entryDN is intended for
making the DN available for attribute value assertions. Thus it is not
mandatory for a LDAP server to make it available as an retrievable
attribute.

The DN is always a part of the entry returned in a search result, just use
it.

Fixes #314

go-sqlite3 takes a long time to compile, so it's very important
to cache a build rather than re-compile every time.

Use go install instead of go build in the build script to cache
all packages. Print a warning in the test script if cached packages
are not found.