Performance improvement and better documentation of examples

fix: memory allocations (#252)

* fix: memory allocations

* fix: replace strings.Builder to bytes.Buffer for old goland versions

* fix: rename escapedStringToEncodedBytes to decodeEscapedSymbols

* feat: remove one allocation

* fix (v3): memory allocations

Add DialURL and ModifyRequest.Increment

add modify-increment extension support detailed in RFC4525 (#227)

* add modify-increment extension support detailed in RFC4525

This extension is detailed in [RFC4525](https://tools.ietf.org/html/rfc4525).
To summarize, it allows for auto-incrementing a specific attribute by a
specific amount. It can be used in conjunction with pre-read, post-read,
and assert control types

* update v3

Use v3 suffix in module name

Update go.mod (#241)

I believe that this (plus a new tag) is what is necessary for native go modules support -- right now go modules complains that the version tag is >= v2 but the module doesn't claim to be a version >= v2.

Fix go.mod

Rename asn1 ber dependency. (#243)

* Rename asn1.ber dependency.

* go mod tidy

* Update travic CI to new asn1 ber

* Update travis go_import_path

Updated go.mod to use github.com instead of gopkg.in

v3.1.1

Use github for module name. (#239)

Add SASL/EXTERNAL mechanism for authentication

Also some internal refactoring to make the code flow more consistent and predictable.

Minor error handling fix

Also some internal Go 1.12 build updates.

Exposing Internals

This release adds a couple goodies in the ldap connection:

• Exposing the ldap.Conn.IsClosing()
• Exposing the ldap.Conn.TLSConnectionState()

v3.0.0

conn: Ensure 64-bit alignment for atomics on 32-bit platforms

Release gopgk.in/ldap.v3

Initial version of gopkg.in/ldap.v3

If you experience issues with this release you can fall back to gopkg.in/ldap.v2